Several months ago my wife and I, along with a friend, drove our new Prius plug-in hybrid 40 miles on state roads to an evening picnic. The battery was fully charged and on arrival the dash board display showed 100 miles per gallon (mpg) for the trip. Being the first local trip out of Oberlin on which I noted the mileage, I was surprised and said to our friend, “That seems high.”

On the way back we were in hybrid mode, which means the car is powered by a gasoline engine as well as an electric motor using electricity generated by the engine and when the car coasts or breaks. Each of us made a guess for the return trip mpg: my wife, 65; our friend, 70; and I guessed what I thought would certainly be too high, 75. Back in Oberlin, the dashboard display showed 73 mpg. We were impressed!

We purchased a Prius plug-in hybrid because we wanted our local travel to be powered by our solar generated electricity. Toyota reports that the Prius can go 13 miles on a fully charged battery before using any gasoline. For local travel we’ve calculated an average of 15 miles per full charge or 4.6 miles/kilowatt hour (kWh). At 10 cents/kWh, the cost would be about 2 cents/mile. In a car that averaged 30 mpg and with gasoline at $3.50/gallon, it would cost 6 times more!

Most of our local travel is less than 10 miles, so on these trips our car is powered by solar electricity. In the last four months (mostly short trips) we filled the gas tank twice, 8.5 gallons each time. In these four months we averaged 106 mpg. On long trips that are in hybrid mode, we’ve averaged 56.2 mpg.

In the Prius, electricity is 3 times more efficient than gasoline. That is, a gallon of gasoline contains the equivalent of 35 kWh of electricity but only moves the car about 56 miles. However, 35 kWh stored in battery form moves the car about 160 miles.

Since purchasing the Prius, we have traveled 7,398 miles using 101 gallons of gasoline which means that 78% of our mileage was powered by gasoline and 22% of it was powered by sunlight. We’re averaging 73 mpg.

Examined from a cost perspective, we’ve spent $321 at an average price of $3.18/gallon. Had we purchased a standard vehicle getting an average 30 mpg, we’d have used 246 gallons or 145 gallons more, saving about $460. And we released no carbon dioxide for about 1,628 of those miles.

Current plug-in hybrids are transition vehicles to fully electric cars that in the future will reduce even further the cost for transportation fuel and carbon dioxide emissions, if the source of the electricity is carbon neutral. Because OMLPS has aggressively pursued carbon neutral sources of electricity, 90% of Oberlin’s electricity will be carbon neutral in 2015. That means electric cars plugged into Oberlin’s grid will cause almost no carbon emissions.

Do electric vehicles have downsides? Yes, of course. Batteries are heavy, expensive, and have to be replaced and recycled. Charging currently takes much more time than pumping gas. Present ranges are limited to just over 100 miles in fully electric cars.

Are electric cars for Oberlin? Yes, plug-in hybrids are perfect for driving around Oberlin and the surrounding area. And fully electric cars are currently an excellent choice except for trips beyond their mileage range. A few fully electric cars are already on the roads. As the Oberlin community addresses the challenge of becoming a climate positive community, electric transportation will certainly play an important role.

Comments

Lisa Kavanaugh
March 16, 2013

On face value electric hybrids save us money on gas, but cost more for repairs. The data out there also shows a large carbon footprint (Hummer-sized) related to the manufacturing process. The damage caused by mining for the minerals needed to make these batterie, as well as our other electronic devices (cell phones, iPads) is not being brought to the forefront. As wise consumers we are learning to research a product from its origins. I feel we've not been taught to do this in the past and often overlook the "hidden" details. We are learning and doing the best we can with the information we are given. My hope is we will dig deeper now that information is so abundant. Information technology has a way of bringing transperancy, like it or not! May we continue to strive toward more sustainable electronics because I do love my laptop and cell phone!